Power Play

Do lithium batteries really stack-up?

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KT Insurance
Dec 10 2021
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By Richard Robertson.

For a long time I’ve played with the idea of lithium power for our small motorhome. Given unlimited funds I would go out today and replace its traditional 100 amp-hour (AH) battery with a lithium equivalent, but who has unlimited funds? For me and perhaps you, money is a consideration and it raises the question: Are lithium batteries worth the cost?

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Lead acid batteries have been the mainstay of RV 12-volt systems since Adam was an apprentice electrician. I’m also sure they will be around for many years to come. The most commonly used type in RV applications is the deep-cycle Absorbent Glass Matt battery, better known as an AGM. Reliable, proven and relatively cheap – a 100 AH AGM is around $300 – they are what you find in most new RVs.

Working out battery capacity requirements isn't rocket science, but the starting point is usable capacity. Depending on who you talk to and what you read, conventional wisdom says you should not run-down any deep-cycle battery below 50 per cent of its rated capacity at most, or more usually, 25 per cent. Basically, the more you run it down the shorter its lifespan. Of course, you can repeatedly run it completely flat – there's no law against it – but the battery won’t last very long.

Let's say you choose to regularly pick the middle ground and use around 33 per cent – that's 33 AH of power from a 100 AH battery. In our small motorhome that comfortably runs our 85-litre, 12-volt compressor fridge overnight, a few LED lights, the TV for a couple of hours if required and the 12-volt fan. It also runs the water pump as needed and even the Webasto diesel heater’s fan through the night. Not bad. Our 12-volt AGM deep-cycle house battery is now just over 5 years old and in that time I've never seen it dip below the green range on the monitor. True, it hasn't had a huge amount of use overall and is charged all-day by solar, but I don't think it's anything special. Given all that, why would I want to upgrade to lithium? Well, can you ever have too much power (and I wouldn’t mind an inverter for the Nespresso machine)?

Anyway, let’s say I’d completely stuffed the battery from repeated deep discharging over three years. Having paid $300 for a new battery that equates to $100 a year for our off-grid power needs. Not bad, and of course it's much better in reality as we sail past five years usage.

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The promise of lithium batteries is tantalising. Not only can you repeatedly use 80 percent of the rated capacity without detriment (that’s the claim), lithium batteries are significantly lighter and longer lasting. But at what cost, and I'm not just talking financial?

Lithium batteries are not without risks. There's a reason airlines ask if you have lithium batteries packed in your luggage, and it's not because they're interested in your portable power preferences. Lithium batteries can be unstable and catch fire, and while there are different types of lithium battery composition and the technology is rapidly advancing, it's worth bearing the safety side in mind. That’s because the temptation is to look for a bargain on eBay. Without casting aspersions on the ethics of industrious Chinese entrepreneurs (well, too much), there are way too many horror stories out there of cheap Chinese lithium batteries that are total rubbish and also potential death traps. Buy them at your peril, but remember, if it seems too good to be true it probably will be…

Next up the ladder are the nice-looking but largely unknown lithium batteries that abound on eBay and the like. Starting around $400 for a 100 AH unit, even if they have good buyer feedback, how do you know it’s not fake and how long have they been in service? I’m thinking there must be some decent quality mid-range lithiums on the market, but you’d have to do a lot of research to be sure of what you’re buying (starting with a reputable seller).

That leaves buying a name brand to be safe. You’re looking around $1000 for something like an EPL-100-12V LITE, the new entry-level lithium battery from market-leader Enerdrive. The company says this battery is equal to a 160 AH AGM, based on discharging it to 80 percent versus 50 percent for an AGM. It also says the battery is nearly 50 percent lighter and 30 percent smaller – both worthwhile considerations (especially if planning a new fit-out). Battery price aside, you also need to add the cost of a lithium-specific battery charger. This can add hundreds of dollars to the changeover and yet is essential for long battery life and safe operation.

There are varying claims regarding the potential lifespan of a lithium battery in an RV, but 2000-plus recharging cycles seems average-to-conservative. That's compared with around 1000 for the AGM. Even given the extended lifetime, by the time you factor in the battery price and charger/management system upgrade, I doubt you're ahead on an annual cost basis. Of course the benefit of lithium in terms of usable power shouldn’t be underestimated, just be sure you really need it before taking the plunge.

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Obviously, you have to balance upfront cost against the usable power again, but also take into account how long you will own the vehicle. There is little point spending thousands on a bells-and-whistles electrical system if the existing one does the job and you're going to sell the vehicle in the next year or two. In fact I can't escape the thought that there is little point spending thousands on a bells-and-whistles electrical system if the existing one does the job, regardless of how long you intend keeping the vehicle.

As I said at the beginning, if money was no object I’d add a lithium battery tomorrow – just because. But money is an object, I’m a pragmatist and our RV is getting on in years. Try as I might, for me the financial equation simply does’t make sense.

However, if you’re looking to upgrade your RV’s 12-volt power system and can make the numbers work, by all means jump on the lithium power wagon. Just make sure the wagon has a reputable brand name on it. But remember, there’s plenty of life left in traditional lead acid battery systems, little risk and ready availability while you travel. The power truly is in your hands, so choose wisely…

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